Quantum coupled oscillators versus forced oscillator
Antonio S. M. de Castro, V. V. Dodonov · Journal of Optics B Quantum and Semiclassical Optics · 2001
We compare the time evolutions of two quantum systems: a quantum harmonic oscillator driven by a classical force and two coupled quantum harmonic oscillators. We find the conditions under which the first system can be considered as a `mean-field approximation' to the second one. This happens in the weak coupling limit provided that the `master' oscillator was initially in a highly excited quantum state with small fluctuations of the canonical variables (such as the coherent state or displaced thermal state), while the `subordinate' oscillator must not be `too excited'. The essential difference between the resonance and nonresonance cases is discussed. In particular, the effect of the resonance-quantum-state exchange is demonstrated.